Monday, April 30, 2018

Each day in England, on average, 141 children enter hospital to have rotten teeth removed, usually under general anaesthetic. They may get a day or so off school, but learning phonics and counting in threes is like a trip to Disneyland in comparison with surgery. Dentists say the rot is preventable in 90% of cases, with dietary habits the obvious culprit. But far more befuddling to modern dentistry is what lies behind the decay in those for whom it isn’t preventable.

Many of these children have what is known, uncatchily, as molar-incisor hypomineralisation (MIH), a condition first recognised in the 80s. It means that the outer enamel on certain teeth does not form properly. Some dentists are reporting a rise in the number of cases they’re seeing, but the condition is still poorly understood. Stephen Fayle, a spokesman for the British Society of Paediatric Dentistry (BSPD), regularly sees the condition in his role as a hospital-based consultant in children’s dentistry in Leeds. He says the data available in the UK suggests that 10% of children are affected. “It’s a considerable, commonly presenting condition,” he says.

When it strikes, MIH affects the first four adult molars, which break through at about six years of age. The condition varies in severity, often with just one tooth affected. But at the most extreme end of the spectrum, a tooth will start crumbling soon after it has erupted. Mild cases will merely incur a slight discoloration. The British Dental Association’s scientific adviser Damien Walmsley says: “The enamel is thinner and softer, and more prone to being dissolved away. The surface allows bacteria to hide in the defects, which means these teeth are more prone to decay.” Fluoride treatments, along with strict brushing and dietary regimes, are the only way to save them.

Even after much academic study, researchers are little the wiser about what causes MIH. Pollution has been suggested, and links have been drawn with, Fayle says, “problems around birth, breathing problems when children have been little, viral infections such as chickenpox. But none of these factors have come out as strongly or very strongly associated with a child having the condition.” However, it is believed that the primary cause is environmental rather than genetic. These molars are formed at birth and undergo a hardening process over the next two or three years; a process Fayle likens to “constructing a sponge and then pumping concrete into it. Something goes wrong, we believe, in those first two years, when that concrete is being pumped in.”However, as any veteran of the bedtime routine will testify, precision tooth-cleaning inside a six-year-old’s mouth is challenging – especially if they have this condition, which, like bad decay, renders affected teeth extremely sensitive. Dental examinations can be unbearable. “They’re only six or seven and have a limited ability to explain what they’re feeling,” says Fayle. “They just don’t like it, and that tends to make them more phobic.”

Dietary deficiencies are unlikely to trigger MIH because you would expect to see a symmetrical effect, whereas this condition has seemingly random coverage. “You can have a tooth on one side that’s perfectly all right and the same tooth on the other side, which developed at exactly the same time, is crumbly.” Even in those with all four affected, one or two will be much worse than the others.

There is an impression, says Fayle, that MIH is a modern disease, but evidence of it has been found in 200- to 300-year-old skeletons. Scandinavian and German researchers have tracked children born in consecutive years, and, rather than charting a steady rise, prevalence goes up and down. “It’s bizarre,” says Fayle. “The worst years had more than twice as many cases as the best years. Nobody can explain that, but it’s almost as if there’s something in the background changing that is making children more susceptible to getting this. It’s a baffling mystery.”

Occasionally, white or yellowish marks also appear on the front adult teeth, but except for rare cases, these only pose a cosmetic problem which, if affecting the child’s wellbeing, can be masked. If a crumbly molar must be removed, all is not lost. “If you get the timing right,” says Fayle, “the second adult molar and wisdom teeth waiting in the gums will usually shunt forwards and take its place.”

But MIH or no MIH, what can parents do to stop the rot? The BSPD is running a “Dental Check by One” campaign, encouraging a dentist visit to check the first teeth as soon as they arrive and ensure parents get the right advice in good time. Dentists believe bad habits start when babies are weaned (12% of children in England have decay at three years). “One of the classic things that parents will do is let children take bottles of milk or juice to bed at night.” At three in the morning, most parents would do anything to get a child back to sleep, but, he says, “once you’ve established that pattern of behaviour, it’s really damaging for the teeth”.

Similarly, letting toddlers carry bottles of juice around all day “is like throwing a bit of petrol on the fire, keeping the decay process going”. Switching to cups instead of bottles and limiting juice to mealtimes helps avoid this. Snacking should be minimised, too, with sweet treats reserved for pudding rather than between meals. “Even things such as crisps that appear to be savoury,” warns Fayle, “stick around your teeth and an enzyme in saliva breaks the starch down to sugar.”

Checking toothpaste has the recommended fluoride levels is also encouraged. For under threes that’s 1000ppm (parts per million), rising to 1350-1500ppm after that. “And the advice now is to spit and not rinse,” says Fayle. By leaving fluoride in your mouth at bedtime, he says, “you’re protecting your teeth and helping them to repair all night”.

Children under three always need an adult to brush for them, but depending on their development, they can start having a go themselves after that. However, it needs to be supervised by the adult up to about age seven, says Fayle.

An exhibition at the Wellcome Collection, Teeth, which opens in London next month, will demonstrate that oral health (just like overall health) has long been a socioeconomic issue. Clare Jones, a lecturer in the history of medicine at the University of Kent, helped put together the exhibition and says: “The north/south divide seems to be particularly stark. In 2012/2013, in north-west England, 33% of five-year-olds had tooth decay, whereas only 20% did in the south-east.” However, her research also highlights how far we have come. “One hundred years earlier, in 1913,” says Jones, “these figures were 80% of children in the north and 60% in the more affluent home counties.”